55 



water. The eggs had been laid about eighteen hours and were left 

 under the water for three days. At the end of this time 8, or 23 per 

 cent, had hatched and 3 larvae remained, drowned in the water, while 

 the other 6 had crawled up into the air and escaped. From this it is 

 evident that the short periods during which eggs are exposed to 

 extreme moisture in nature cd.n have but little influence on them. 



EGGS DESTROYED BY STORMS. 



A very important factor, however, and one which undoubtedly 

 causes the destruction of immense numbers of eggs, is the mechanical 

 force of the rain during violent storms. Although they are rather 

 firmly attached, the combined effects of rain, wind, and sandy parti- 

 cles washed against the plants removes many eggs. On two occasions 

 during the spring. May 16 and May 29, plants in the laboratory gar- 

 den known to have had eggs on them were examined after the rains 

 and most of the eggs were found to be missing. Regarding field con- 

 ditions, no positive data are at hand, but the unusual scarcity of eggs 

 on corn after hard rains was evident on several occasions. 



EFFECT OF SUN ON EGGS. 



There is an opinion held among many planters that a large number 

 of eggs, when laid on exposed portions of the plant, are destroyed by 

 the rays of the hot midsummer sun. This led us to try the experi- 

 ment of subjecting eggs to the direct rays of the sun. On August 30 

 a lot of 20 eggs which had been laid on a dried cotton leaf were pinned 

 high up on a cotton plant, where they were in continuous sunshine 

 during the day. All hatched after the normal period. Again, a few 

 days later a moth was caged over a few leaves of a growing cotton 

 plant, and some 50 eggs were laid on the upper sides of the leaves. 

 After this the cage was removed and the leaves slanted so as to receive 

 the perpendicular rays of the sun. The eggs were in no way injured, 

 however, and practically all of them hatched normally. 



THE LARVA. 



When the young larva hatches from the ef!;g it is scarcely over a 

 millimeter in length, and during growth it molts or sheds the skin six 

 times before becoming a pupa or chrysalis. Very exceptionally one 

 of these molts may be omitted, the bollworm pupating after only five 

 molts. Each successive instar is larger, and the larva grows more 

 and more' rapidly as it nears maturity. The larvae were carefully 

 studied by Mr. Girault during the course of his breeding work, and 

 the technical descriptions included in the following account have been 

 prepared by him from notes made at that time. 



